D-Serine/D-alanine/glycine/D-cycloserine:H+ symporter (regulated by the small RNA, GcvB; Pulvermacher et al., 2009). The system is active after growth in minimal medium but not after growth in complex medium (Baisa et al. 2013).

Putrescine:ornithine antiporter for putrescine export; putrescine:H+ symporter for uptake (Igarashi and Kashiwagi 1996). Modeling tools have been used to gain information about the structures and functions of CadB and PotE in E. coli (Tomitori et al., 2012).

The thiamine (vitamin B1) transporter, Thi9 (SPAC9.10). Uptake is inhibited by pyrithiamine, oxythiamine, amprolium, and the thiazole part of thiamine indicating that these compounds are substrates of Thi9 (Vogl et al., 2008).

Glutamate:γ-aminobutyrate antiporter of 477 aas and 12 TMSs, GadC. Expression of gadCB in L. lactis in the presence of chloride is increased when the culture pH decreases to low levels,
while glutamate stimulated gadCB expression (Sanders et al. 1998). These
genes encode a glutamate-dependent acid resistance mechanism that is optimally active when needed for acid neutralization.

The Asc-type small neutral L-amino acid:H+ symport transporter-2 (Asc-2). Does not associate with 4F2hc or rBAT, but probably associates with some comparable heavy chain. Doesn't transport some substrates of Asc-1 such as α-aminoisobutyric acid and β-alanine (Chairoungdua et al., 2001)

General amino acid permease (all L-amino acids and some D-amino acids as well as β-alanine, polyamines and GABA). Systematic mutational analysis of the intracellular regions of yeast Gap1 permease revealed multiple intracellular regions involved in its secretion, transport activity, and down-regulation (Igarashi and Kashiwagi 2010; Merhi et al., 2011). GAP1 is a "transceptor", fuctioning in both transport and reception, necessary for cAMP-independent
activation of the Protein Kinase A pathway under conditions of re-addition of
amino acids to cells previously starved for amino acids (Diallinas 2017).

Golgi polyamine/paraquot uptake transporter of 478 aas, LAT4. Also called PUT2 and PAR1. Mutations give rise to paraquot resistance (Par1) both in A. thaliana and in rice. Probably present in the chloroplast membrane (Fujita and Shinozaki 2014).

APC family member; Ala/Val/Leu-rich protein encoded within an operon that also encodes a 23S rRNA methyl transferase, RumA. Two half sized TrkA proteins are encoded within an operon that is divergently transcribed. Possibly, they regulate transport.